Resumen
[0001] A method of controlling the operation of a multi-cell switching power converter (10) is provided. The power converter (10) comprises at least two converter legs (31, 32, 33) connected in parallel, each converter leg (31, 32, 33) including at least one converter cell (20) that is operated in accordance with a switching sequence that includes transitions between predetermined switching states (26, 27, 28) and that generates a current waveform (51, 52, 53) in the converter leg. The method includes operating the power converter (10) in an interleaving mode in which each converter leg (31, 32, 33) is operated with a switching sequence having a different phase, generating a periodic reference signal (40), and controlling the phase shift between the switching sequences of the two or more converter legs (31, 32, 33) by detecting, for each converter leg (31, 32, 33), an intersection (45) between the current waveform (51, 52, 53) generated by the converter leg (31, 32, 33) and the periodic reference signal (40). Upon detecting the intersection of the current waveform (51, 52, 53) of a converter leg (31, 32, 33) with the reference signal (40), a transition to a predetermined switching state (28) of the switching sequence is triggered.
Reivindicaciones
1. Patent claims 1. A method of controlling the operation of a multi-cell switching power converter (10), wherein the power converter (10) comprises at least two converter legs (31, 32, 33) con nected in parallel, each converter leg (31, 32, 33) including at least one converter cell (20) that is operated in accord ance with a switching sequence that includes transitions be tween predetermined switching states (26, 27, 28) and that generates a current waveform (51, 52, 53) in the converter leg, wherein the method comprises: operating the power converter (10) in an interleaving mode in which the switching sequence of each of the con verter legs (31, 32, 33) is phase shifted with respect to the switching sequences of the one or more other con verter legs so that each converter leg (31, 32, 33) is operated with a switching sequence having a different phase and generates a current waveform (51, 52, 53) hav ing a corresponding phase shift; generating a periodic reference signal (40), wherein the periodicity of the reference signal (40) is determined based on the number of different phases; and controlling the phase shift between the switching se quences of the two or more converter legs (31, 32, 33) by detecting, for each converter leg (31, 32, 33), an intersection (45) between the current waveform (51, 52, 53) generated by the converter leg (31, 32, 33) and the reference signal (40), and upon detecting the intersec tion of the current waveform (51, 52, 53) of a converter leg (31, 32, 33) with the reference signal (40), trig gering for this converter leg (31, 32, 33) a transition to a predetermined switching state (28) of the switching sequence. 2. The method according to claim 1, wherein the period of the switching sequence is variable and allowed to vary during op eration, wherein the method preferably further comprises de riving from a trigger value (iref) for triggering the transi- tion to a subsequent switching state a target period of the switching sequence and, upon a change of the trigger value (iref), adapting the period of the reference signal in ac cordance with a resulting change of the target period of the switching sequence. 3. The method according to claim 1 or 2, wherein the periodic reference signal (40) is a sawtooth-shaped signal comprising repeating ramps. 4. The method according to claim 3, wherein within one period (T) of the switching sequence, the reference signal (40) com prises one ramp (41, 42, 43) for each converter leg (31, 32, 33). 5. The method according to any of the preceding claims, wherein the method further comprises obtaining a reference current (iref) for the transition to the switching state (28), and determining a period (T) of the switching sequence based on the reference current (iref) and the current wave form (51, 52, 53). 6. The method according to any of the preceding claims, wherein the reference signal (40) is generated based on an upper limit (i<t)>and a lower limit (i<p)>, wherein generating the reference signal (40) comprises generating a ramp from the upper limit (i<t)>to the lower limit (i<p)>and resetting the ramp upon reaching the lower limit (i<p)>, or generating a ramp from the lower limit (i<p)>to the upper limit (i<t)>and resetting the ramp upon reaching the upper limit (i<t)>. 7. The method according to claim 5 and 6, wherein generating the periodic reference signal (40) comprises setting a slope (a) of the ramp to a predetermined value (mi) and deriving the upper limit (i<t)>and the lower limit (i<p)>based on the current reference (iref) and the period (T) of the switching sequence, or wherein generating a periodic reference signal (40) com prises setting the upper limit (i<t)>and the lower limit (i<p)>such that the current reference (iref) lies between the upper limit (i<t)>and the lower limit (i<p)>and deriving a slope (a) of the ramp based on the period (T) of the switching se quence. 8. The method according to any of the preceding claims, wherein for each converter leg (31, 32, 33), the transition from a last switching state of the switching sequence to a first switching state of the next switching sequence occurs at a zero crossing of an inductor current of the converter cell (20) of the respective converter leg (31, 32, 33). 9. The method according to any of the preceding claims, wherein said switching sequence corresponds to an operation of the power converter in a modulation mode, wherein the mod ulation mode is a boundary conduction mode or is a three- stage conduction mode in which the current waveform includes a first section (A) of rising current, a second section (B) of rising, falling or constant current and a third section (C) of falling current. 10. The method according to claim 9, wherein the modulation mode is the three-stage conduction mode, wherein the transi tion that is triggered corresponds to the transition from the second section (B) to the third section (C) of the current waveform (51, 52, 53), wherein preferably, the power convert er (10) is operable in a buck mode in which the second sec tion (B) of the current waveform corresponds to a rising cur rent and in which the reference signal (40) is generated as a sequence of repeating leading edge ramps, and/or is operable in a boost mode in which the second section (B) corresponds to a falling current and in which the reference signal (40) is generated as a sequence of repeating trailing edge ramps. 11. The method according to any of the preceding claims, wherein the periodic reference signal (40) comprises a se- quence of a repeating reference waveform (41, 42, 43), where in within the duration of one period (T) of the switching se quence, the reference signal (40) comprises one reference waveform (41, 42, 43) per converter leg (31, 32, 33), the reference waveform being associated with the respective con verter leg, and wherein detecting an intersection (45) be tween the current waveform (51, 52, 53) of each converter leg (31, 32, 33)and the periodic reference signal (40) comprises detecting the intersection (45) between the current waveform (51, 52, 53) of the converter leg (31, 32, 33) and the refer ence waveform (41, 42, 43) associated with the converter leg (31, 32, 33). 12. The method according to claim 11, wherein the method com prises counting the reference waveforms (41, 42, 43) in the reference signal (40) using a counter (46), associating each converter leg (31, 32, 33) with a different count and detect ing the intersection (45) of the reference signal (40) with the current waveform (51, 52, 53) of a converter leg (31, 32, 33) only for the reference waveform (41, 42, 43) of the ref erence signal (40) corresponding to the count associated with the respective converter leg (31, 32, 33). 13. A controller of a multi-cell switching power converter, wherein the power converter (10) comprises at least two con verter legs (31, 32, 33) connected in parallel and providing a phase shifted output current, each converter leg (31, 32, 33) including at least one converter cell (20) that is oper ated in accordance with a switching sequence that includes transitions between predetermined switching states (26, 27, 28) and that generates a current waveform (51, 52, 53) in the converter leg (31, 32, 33), wherein the controller (80) is configured to perform the method according to any one of the preceding claims. 14. A multi-cell switching power converter comprising least two converter legs (31, 32, 33) connected in parallel and providing a phase shifted output current, wherein the power converter (10) further comprises a controller (80) according to claim 13. 15. A computer program for controlling the operation of a multi-cell switching power converter (10), wherein the com puter program comprises control instructions which, when exe cuted by a processing unit (81) of a controller (80) of the power converter (10), cause the processing unit (81) to per form the method of any of claims 1-12.
